EP0060681B1 - A combustible gas analyzer - Google Patents
A combustible gas analyzer Download PDFInfo
- Publication number
- EP0060681B1 EP0060681B1 EP19820301229 EP82301229A EP0060681B1 EP 0060681 B1 EP0060681 B1 EP 0060681B1 EP 19820301229 EP19820301229 EP 19820301229 EP 82301229 A EP82301229 A EP 82301229A EP 0060681 B1 EP0060681 B1 EP 0060681B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- gas
- valve
- air
- combustible gas
- analyzer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- 239000007789 gas Substances 0.000 claims description 67
- 238000002485 combustion reaction Methods 0.000 claims description 42
- 239000001301 oxygen Substances 0.000 claims description 18
- 229910052760 oxygen Inorganic materials 0.000 claims description 18
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 17
- 239000000203 mixture Substances 0.000 claims description 11
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims description 10
- 229910001928 zirconium oxide Inorganic materials 0.000 claims description 9
- 230000000694 effects Effects 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 5
- 238000001514 detection method Methods 0.000 claims description 3
- 238000012544 monitoring process Methods 0.000 claims description 3
- 239000000446 fuel Substances 0.000 description 15
- 238000005259 measurement Methods 0.000 description 11
- 239000002737 fuel gas Substances 0.000 description 8
- 230000005484 gravity Effects 0.000 description 8
- 239000000047 product Substances 0.000 description 5
- 230000001276 controlling effect Effects 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 230000004044 response Effects 0.000 description 4
- 230000001419 dependent effect Effects 0.000 description 3
- 230000008859 change Effects 0.000 description 2
- 230000000875 corresponding effect Effects 0.000 description 2
- 230000000977 initiatory effect Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 150000002926 oxygen Chemical class 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/50—Investigating or analyzing materials by the use of thermal means by investigating flash-point; by investigating explosibility
- G01N25/54—Investigating or analyzing materials by the use of thermal means by investigating flash-point; by investigating explosibility by determining explosibility
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/12—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using combustion
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0011—Sample conditioning
- G01N33/0013—Sample conditioning by a chemical reaction
Definitions
- the present invention is directed to a combustible gas analyzer and more specifically, to a gas analyzer for determining the heating Wobbe Index of combustible gases and a method for analysing such a gas.
- One method of determining the Wobbe Index of the gas involves the combination of calorimeter, a density meter and a computing circuit, e.g., a microprocessor. These parts, while they may be combined into a single instrument, produce an overall device which is very costly and exhibits a sluggish operation whereby rapid changes in the gas mixture are measured at a slow rate and the resulting correction, if necessary, is also applied at a corresponding slow rate.
- One apparatus for producing this type of operation includes a sampling line containing a flow control nozzle for withdrawing a gas sample, a means for adjusting the gas sample so that the pressure difference through this control nozzle has an adjustable constant value, a means for feeding a constant volume of air into the gas stream sample, a combustion chamber, a burner in the combustion chamber to completely burn the gas-air mixture, an outlet for the burned gas from the combustion chamber and an oxygen sensor in the combustion chamber to sense the oxygen content of the exhaust gas.
- This oxygen content is a quantity which is correlated to the Wobbe Index of the measured gas.
- the thermal delivery rate i.e.
- the measuring apparatus providing such a Wobbe Index measurement would provide an efficient means of "feed forward" control to a furnace requiring a constant BTU per minute input without regard to changes in gas supply composition, density and kJ content.
- the means for producing the required adjustable but constant flow rates i.e. means for producing a flow rate which is adjustable but is constant for any given setting of the adjustment
- means for producing a flow rate which is adjustable but is constant for any given setting of the adjustment is known from for example GB-A-1 555 224 (where that means is used to control a common supply to a pair of feed pipes, to which variable amounts of air are fed, and which feed a pair of burners, the system including feedback means to keep the temperature different between the two . flames constant).
- EP-A1-8151 also describes a fuel control system in which the Wobbe Index of a mixture of fuels is measured, and the ratio of different fuels is varied accordingly so as to maintain the Wobbe Index constant.
- the known Wobbe Index measuring system of EP-A1-8151 preferably requires a cheap and efficient oxygen sensor, and a convenient form of oxygen sensor is the zirconium oxide type (known from, for example, DE-B-2 400 246).
- a convenient form of oxygen sensor is the zirconium oxide type (known from, for example, DE-B-2 400 246).
- this type of sensor we have found that its output is decidedly temperature sensitive.
- the known system therefore suffers from the drawback that the temperature of the combustion gases has to be controlled to a constant value (or the temperature has to be sensed and used to correct the oxygen sensor output).
- the invention provides a combustible gas analyzer for determining the Wobbe Index of said gas comprising: means for supplying air and combustible gas at controlled flow rates; means for mixing the air and combustible gas; combustion means for burning the mixture; and a detector for detecting the oxygen content of the combustion products, characterized by: a valve for controlling the flow of combustible gas to the mixing means; control means responsive to the detector to control the valve to achieve an oxygen content of the combustion products corresponding to substantially stoichiometric combustion; and a monitor for monitoring the gas flow restricting effect of the valve to enable the detection or indication of the Wobbe Index of said combustible gas.
- a method for analyzing a combustible gas to determine the Wobbe Index of the gas is provided as disclosed in claim 7.
- FIGS. 1 and 2 are pictorial illustrations of two combustible gas analyzers according to the present invention for measuring the Wobbe Index of the gas.
- the gas analyzer is supplied with air and combustible gas through pipelines 2 and 10.
- the pipeline 2 is connected to the input of a first conventional pressure regulator 4 while the output of the pressure regulator4 is connected to an output pipeline 6.
- the output pipeline 6 is connected to one input of a mixing valve 8.
- the pipeline 6 is arranged to contain a fixed orifice or restriction (not shown) which is the dominating downstream restriction in the flowline supplied by the output of the pressure regulator 4.
- a fixed orifice provides a means for achieving a steady flow rate of the air from the pressure regulator 4 to form a steady flow rate air supply.
- a supply (not shown) of a combustible gas is arranged to supply a fuel gas through the second input pipeline 10 connected to the input of a second conven- . tional pressure regulator 12.
- the output of the second pressure regulator 12 is supplied through an output pipeline 14 to a control valve 16.
- the valve 16 is arranged to provide an orifice which, while variable, is the dominating downstream restriction in the flowline supplied by the output of the second pressure regulator 12. Since a variation in the flow rate of the fuel gas is desired, a different steady flow rate is achieved for each stable setting of the valve 16 in a similar way to that provided by the orifice in the pipeline 6.
- the output of the control valve 16 is supplied through an output pipeline 18 to a second input of the mixing valve.
- An output of the mixing valve 8 is supplied through pipeline 20 to a burner jet 22 for producing a combustion flame 24.
- the burner jet 22 and the combustion flame 24 are located within a housing 26 providing a combustion chamber for the combustion flame 24. Also located within the housing 26 would be means for initiating the burning of the combustible gas by means of a spark or other device and means for detecting the presence of the flame 24 to provide a control for the flame initiating device. Such devices are well-known and accordingly have not been shown.
- the exhaust gases from the combustion chamber 26 are allowed to escape through a restricted opening 28 in the wall of the combustion chamber 26.
- a well-known zirconium oxide detector 30 is located adjacent to the flame 24 to effect a detection of the oxygen content of the end products of the combustion process to determine a preselected combustion state, e.g. stoichiometric combustion.
- the output of the zirconium oxide detector 30 is applied over an output line 32 to an input of a data processing system 34 which may incorporate a microprocessor.
- the valve 16 is driven by a valve motor 36 connected thereto through a valve stem 38.
- the valve stem 38 is connected to an apparatus for providing an indication of the position of the valve stem 38.
- An example of an apparatus for providing such an indication includes a lever arm 40 attached to the valve stem 38 and arranged to drive the slider 46 of a potentiometer across the resistance element 44 of a potentiometer.
- the resistance element 44 of the potentiometer is connected by electrical lines 48 and 50 to the data processor 34 while the slider 46 is connected by an electrical line 52 to the data processor 34.
- the data processor 34 is arranged to use the input signal from the zirconium oxide detector 30 to produce a control signal on output line 54 for controlling the operation of the valve motor 36.
- the data processor 34 may be used to produce an output signal in response to a signal from the potentiometer 42 on a data output line 56 which is connected to a recorder display 58 for displaying the position of the valve stem 38 as an indication of the Wobbe Index of the fuel gas supplied over the fuel inlet line 10.
- the air supply controlled through the first pressure regulator 4 is supplied to the mixing valve 8 at a constant flow rate in combination with the fuel gas supplied through the second pressure regulator 12 and the control valve 16.
- the combustion of the fuel gas in the presence of the air is effected by the flame 24 in the combustion chamber 26.
- the oxygen content of the combustion products or gases is detected by the zirconium oxide detector 30. Since the control valve 16 functions as a variable orifice, the output signal supplied to the recorder display 58 on output line 56 which is representative of the position of the valve motor 36 is a measurement of the Wobbe Index of the fuel gas. This is the result of having a short orifice which produces an effect dependent on the specific gravity of the fluid flowing therethrough.
- variable orifice produced by the valve 16 is the only significant restriction prior to the burner 22 in the flowline containing the valve 16.
- the calorific value e.g., kJ of the gas being burned at the burner 22 will be altered if fuels of different specific gravity are introduced from the fuel line 10.
- the measurement of the movement of the valve stem 38 is dependent on the square root of the specific gravity of the fuel relative to air and the calorific content and is, therefore, a direct indication of the Wobbe Index.
- the value 16 is operated by the data processor 34 by means of the valve motor 36 and valve stem 38 to produce a desired combustion state which is at or near stoichiometric combustion at the flame 24, as discussed more fully later. It should be noted that this desired combustion state is only one point on the combustion curve, and only a repeatability is necessary by returning to the same point for each measurement.
- the combustion level is detected by the sensor 30 as a result of the minimal amount of oxygen remaining in the combustion products from the flame 24.
- the representation of the Wobbe Index i.e., valve position, may be displayed on a suitable display or recorded as a record of the Wobbe Index of the fuel gas since the recorder display 58 may include a hard copy recorder as well as a display apparatus, e.g., cathode ray tube (CRT).
- a display apparatus e.g., cathode ray tube (CRT).
- the pressure regulators 4 and 12 are each provided with a feed back line for supplying a pressure feedback signal from T connectors in lines 8 and 18 respectively back to the regulators for controlling the pressure output thereof.
- the analyzer/ operator is made independent of specific gravity.
- any change in specific gravity would readjust the pressure equilibrium of the regulator 12 to compensate for a specific gravity whereby the valve stem position is a measure of the Wobbe Index. It should be noted that, since the accuracy of the Wobbe Index measurement is dependent on specific gravity of the fuel gas, the proportion of non-combustible gases therein, e.g., helium will effect the accuracy of the measurement.
- the relationship is an inversely proportional one, i.e., the greater the quantity of non-combustible elements, the lower will be the measurement accuracy.
- the non-combustible content is very small which provide a high measurement accuracy of the Wobbe Index, e.g., 1%.
- the analyzer includes a sample fuel inlet 110 which, with calibration gas inlet 111, is adapted to supply either sample fuel or calibration gas to the system from suitable sources thereof as through an electrically controlled two- position, three-way valve 112 which admits the selected components to the system through pressure regulator 113.
- a flow control valve 114 which may be any suitable type of flow control valve which can be accurately modulated electrically, such as a needle valve, is provided to control the sample flow input to the system.
- a metering orifice 115 in conjunction with a sensitive orifice pressure transducer 116 is utilized to accurately measure the sample fuel input to the system.
- Combustion air is applied to the system through an air inlet 117, which may be supplied from a combustion air blower or other source of pressurized air.
- the pressure is regulated by pressure regulator 118 which is backloaded from the common air-gas line 119 as at 120 and a metering orifice 121.
- the sample burner is supplied with the air-gas mixture through line 123 and the products of combustion are sensed as by sensor 124, preferably of Zirconium Oxide (Zr0 2 ).
- the necessary control and data processing functions are performed by electronics shown at 125 and the Wobbe Index output, which may be in the form of a digital register, recorder, direct controller or other means is indicated at 126.
- sensor output is decidely temperature sensitive in the presence of more than minute amounts of oxygen.
- the temperature of the sensor should also be carefully controlled.
- the output is substantially stable over a wide temperature range, i.e., from about 800°C to 1400°C, and therefore temperature control in the combustion chamber is not critical.
- the relative size of the combustion chamber 26 or 122 is normally sized in accord with the amount of fuel to be burned such that the temperature within the chamber is maintained within the limits where the sensor is not temperature sensitive at or about the stoichiometric point of combustion.
- the Zr0 2 sensor of Figures 1 and 2 can be stabilized with amounts of CaO or Y 2 0 3 to further stabilize the temperature related response and to enhance the chemical and physical stability of the Zirconium Oxide for use as a sensor. This results in a stable sensor which possesses almost a step- change response at, or about the point of mixture stoichiometry.
- the fuel flow rate can be accurately controlled by the motorized needle valve 114 in conjunction with the orifice 115.
- the air is also suitably pressure regulated as seen in that figure.
- the sensor 124 is used in conjunction with the electronics to achieve and maintain substantially stoichiometric proportions for the combustion of the sample gas by controlling the fuel flow.
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Description
- The present invention is directed to a combustible gas analyzer and more specifically, to a gas analyzer for determining the heating Wobbe Index of combustible gases and a method for analysing such a gas.
- The well-known Wobbe Index of a combustible gas is defined as the amount of heat released by a burner of constant orifice, McGraw-Hill Dictionary of Science, 1979 and stated mathematically by the following relation:
- W = HIVS-G where H is the caloric combustion value of the gas per unit volume, e.g. kJ/m3, and SG is specific gravity of the combustible gas relative to air. The Wobbe Index is a quantity used in heating technology since different combinations of gases supplied to a gas heated apparatus under the same pressure will provide equal heat production from the apparatus, whereby the apparatus does not need to be readjusted, as long as the Wobbe Index is maintained at a predetermined value. For example, if a mixture of gases from different sources is burned in an industrial heating operation, the gases must be mixed in such proportion that a gas is obtained having a constant Wobbe Index.
- One method of determining the Wobbe Index of the gas involves the combination of calorimeter, a density meter and a computing circuit, e.g., a microprocessor. These parts, while they may be combined into a single instrument, produce an overall device which is very costly and exhibits a sluggish operation whereby rapid changes in the gas mixture are measured at a slow rate and the resulting correction, if necessary, is also applied at a corresponding slow rate.
- It has been discovered that when gas mixtures having different compositions and different Wobbe indices are burned with equal quantities of air, the oxygen content of the exhaust gas show a direct correlation with the Wobbe Index. Accordingly, for purposes'of measurement and control, it is not necessary to measure the Wobbe Index as such and it is sufficient to measure only the oxygen content in the exhaust gas. One apparatus for producing this type of operation is known from EP-A1-8151, and includes a sampling line containing a flow control nozzle for withdrawing a gas sample, a means for adjusting the gas sample so that the pressure difference through this control nozzle has an adjustable constant value, a means for feeding a constant volume of air into the gas stream sample, a combustion chamber, a burner in the combustion chamber to completely burn the gas-air mixture, an outlet for the burned gas from the combustion chamber and an oxygen sensor in the combustion chamber to sense the oxygen content of the exhaust gas. This oxygen content is a quantity which is correlated to the Wobbe Index of the measured gas. However, by actually measuring or providing a quantity which represents the Wobbe Index the thermal delivery rate, i.e. kJ/min, could be obtained to control the industrial heating operation. Thus, the measuring apparatus providing such a Wobbe Index measurement would provide an efficient means of "feed forward" control to a furnace requiring a constant BTU per minute input without regard to changes in gas supply composition, density and kJ content.
- The means for producing the required adjustable but constant flow rates (i.e. means for producing a flow rate which is adjustable but is constant for any given setting of the adjustment) is known from for example GB-A-1 555 224 (where that means is used to control a common supply to a pair of feed pipes, to which variable amounts of air are fed, and which feed a pair of burners, the system including feedback means to keep the temperature different between the two . flames constant).
- The cited specification EP-A1-8151 also describes a fuel control system in which the Wobbe Index of a mixture of fuels is measured, and the ratio of different fuels is varied accordingly so as to maintain the Wobbe Index constant.
- The known Wobbe Index measuring system of EP-A1-8151 preferably requires a cheap and efficient oxygen sensor, and a convenient form of oxygen sensor is the zirconium oxide type (known from, for example, DE-B-2 400 246). However, if this type of sensor is used, we have found that its output is decidedly temperature sensitive. The known system therefore suffers from the drawback that the temperature of the combustion gases has to be controlled to a constant value (or the temperature has to be sensed and used to correct the oxygen sensor output).
- We have discovered that if the flow rate of the fuel is controlled to as to achieve substantially stoichoimetric combustion, the temperature sensitivity of a zirconium oxide type sensor is substantially reduced. Furthermore, we have discovered that under such conditions, particular forms of such sensors gives still further reduced temperature sensitivity.
- Accordingly the invention provides a combustible gas analyzer for determining the Wobbe Index of said gas comprising: means for supplying air and combustible gas at controlled flow rates; means for mixing the air and combustible gas; combustion means for burning the mixture; and a detector for detecting the oxygen content of the combustion products, characterized by: a valve for controlling the flow of combustible gas to the mixing means; control means responsive to the detector to control the valve to achieve an oxygen content of the combustion products corresponding to substantially stoichiometric combustion; and a monitor for monitoring the gas flow restricting effect of the valve to enable the detection or indication of the Wobbe Index of said combustible gas.
- According to another aspect of the invention a method for analyzing a combustible gas to determine the Wobbe Index of the gas is provided as disclosed in claim 7.
- An embodiment of the present invention will now be described in connection with the accompanying drawings, in which the Figures 1 and 2 are pictorial illustrations of two combustible gas analyzers according to the present invention for measuring the Wobbe Index of the gas.
- Referring to the Figure 1, the gas analyzer is supplied with air and combustible gas through
pipelines 2 and 10. The pipeline 2 is connected to the input of a first conventional pressure regulator 4 while the output of the pressure regulator4 is connected to anoutput pipeline 6. Theoutput pipeline 6 is connected to one input of amixing valve 8. In a conventional fashion, thepipeline 6 is arranged to contain a fixed orifice or restriction (not shown) which is the dominating downstream restriction in the flowline supplied by the output of the pressure regulator 4. Such a fixed orifice provides a means for achieving a steady flow rate of the air from the pressure regulator 4 to form a steady flow rate air supply. Concurrently, a supply (not shown) of a combustible gas is arranged to supply a fuel gas through thesecond input pipeline 10 connected to the input of a second conven- .tional pressure regulator 12. The output of thesecond pressure regulator 12 is supplied through anoutput pipeline 14 to acontrol valve 16. As in the case of the previously mentioned orifice in thepipeline 6, thevalve 16 is arranged to provide an orifice which, while variable, is the dominating downstream restriction in the flowline supplied by the output of thesecond pressure regulator 12. Since a variation in the flow rate of the fuel gas is desired, a different steady flow rate is achieved for each stable setting of thevalve 16 in a similar way to that provided by the orifice in thepipeline 6. The output of thecontrol valve 16 is supplied through anoutput pipeline 18 to a second input of the mixing valve. - An output of the
mixing valve 8 is supplied throughpipeline 20 to aburner jet 22 for producing acombustion flame 24. Theburner jet 22 and thecombustion flame 24 are located within ahousing 26 providing a combustion chamber for thecombustion flame 24. Also located within thehousing 26 would be means for initiating the burning of the combustible gas by means of a spark or other device and means for detecting the presence of theflame 24 to provide a control for the flame initiating device. Such devices are well-known and accordingly have not been shown. The exhaust gases from thecombustion chamber 26 are allowed to escape through a restrictedopening 28 in the wall of thecombustion chamber 26. The aforesaid restrictions provided by the fixed restriction in thepipeline 6 and by the variable restriction of thevalve 16 are each effective to provide a greater restrictive effect than that imposed by the other flowline elements, as previously mentioned, including the flow impediments imposed by themixing connector 8, theburner 22 and theexhaust port 28. A well-knownzirconium oxide detector 30 is located adjacent to theflame 24 to effect a detection of the oxygen content of the end products of the combustion process to determine a preselected combustion state, e.g. stoichiometric combustion. The output of thezirconium oxide detector 30 is applied over anoutput line 32 to an input of adata processing system 34 which may incorporate a microprocessor. - The
valve 16 is driven by avalve motor 36 connected thereto through avalve stem 38. Thevalve stem 38 is connected to an apparatus for providing an indication of the position of thevalve stem 38. An example of an apparatus for providing such an indication includes alever arm 40 attached to thevalve stem 38 and arranged to drive theslider 46 of a potentiometer across the resistance element 44 of a potentiometer. The resistance element 44 of the potentiometer is connected byelectrical lines data processor 34 while theslider 46 is connected by anelectrical line 52 to thedata processor 34. Thedata processor 34 is arranged to use the input signal from thezirconium oxide detector 30 to produce a control signal onoutput line 54 for controlling the operation of thevalve motor 36. Concurrently, thedata processor 34 may be used to produce an output signal in response to a signal from the potentiometer 42 on adata output line 56 which is connected to arecorder display 58 for displaying the position of thevalve stem 38 as an indication of the Wobbe Index of the fuel gas supplied over thefuel inlet line 10. - In operation, the air supply controlled through the first pressure regulator 4 is supplied to the
mixing valve 8 at a constant flow rate in combination with the fuel gas supplied through thesecond pressure regulator 12 and thecontrol valve 16. The combustion of the fuel gas in the presence of the air is effected by theflame 24 in thecombustion chamber 26. The oxygen content of the combustion products or gases is detected by thezirconium oxide detector 30. Since thecontrol valve 16 functions as a variable orifice, the output signal supplied to therecorder display 58 onoutput line 56 which is representative of the position of thevalve motor 36 is a measurement of the Wobbe Index of the fuel gas. This is the result of having a short orifice which produces an effect dependent on the specific gravity of the fluid flowing therethrough. In the combustible gas measuring arrangement described above, the variable orifice produced by thevalve 16 is the only significant restriction prior to theburner 22 in the flowline containing thevalve 16. In such an arrangement, the calorific value, e.g., kJ of the gas being burned at theburner 22 will be altered if fuels of different specific gravity are introduced from thefuel line 10. In other words since:valve stem 38 is dependent on the square root of the specific gravity of the fuel relative to air and the calorific content and is, therefore, a direct indication of the Wobbe Index. Thevalue 16 is operated by thedata processor 34 by means of thevalve motor 36 andvalve stem 38 to produce a desired combustion state which is at or near stoichiometric combustion at theflame 24, as discussed more fully later. It should be noted that this desired combustion state is only one point on the combustion curve, and only a repeatability is necessary by returning to the same point for each measurement. The combustion level is detected by thesensor 30 as a result of the minimal amount of oxygen remaining in the combustion products from theflame 24. The representation of the Wobbe Index, i.e., valve position, may be displayed on a suitable display or recorded as a record of the Wobbe Index of the fuel gas since therecorder display 58 may include a hard copy recorder as well as a display apparatus, e.g., cathode ray tube (CRT). - In a modification (not shown), the
pressure regulators 4 and 12 are each provided with a feed back line for supplying a pressure feedback signal from T connectors inlines valve 16, the analyzer/ operator is made independent of specific gravity. Thus, any change in specific gravity would readjust the pressure equilibrium of theregulator 12 to compensate for a specific gravity whereby the valve stem position is a measure of the Wobbe Index. It should be noted that, since the accuracy of the Wobbe Index measurement is dependent on specific gravity of the fuel gas, the proportion of non-combustible gases therein, e.g., helium will effect the accuracy of the measurement. Specifically, the relationship is an inversely proportional one, i.e., the greater the quantity of non-combustible elements, the lower will be the measurement accuracy. However, in a real life application of the present analyzer, e.g., gas user measurements, the non-combustible content is very small which provide a high measurement accuracy of the Wobbe Index, e.g., 1%. - In a second embodiment of the invention, shown in Figure 2, the analyzer includes a
sample fuel inlet 110 which, withcalibration gas inlet 111, is adapted to supply either sample fuel or calibration gas to the system from suitable sources thereof as through an electrically controlled two- position, three-way valve 112 which admits the selected components to the system throughpressure regulator 113. Aflow control valve 114, which may be any suitable type of flow control valve which can be accurately modulated electrically, such as a needle valve, is provided to control the sample flow input to the system. Ametering orifice 115 in conjunction with a sensitiveorifice pressure transducer 116 is utilized to accurately measure the sample fuel input to the system. Combustion air is applied to the system through anair inlet 117, which may be supplied from a combustion air blower or other source of pressurized air. The pressure is regulated bypressure regulator 118 which is backloaded from the common air-gas line 119 as at 120 and ametering orifice 121. The sample burner is supplied with the air-gas mixture throughline 123 and the products of combustion are sensed as bysensor 124, preferably of Zirconium Oxide (Zr02). The necessary control and data processing functions are performed by electronics shown at 125 and the Wobbe Index output, which may be in the form of a digital register, recorder, direct controller or other means is indicated at 126. - It has been found that sensor output is decidely temperature sensitive in the presence of more than minute amounts of oxygen. Thus, when operating in the oxygen rich portion of the Zr02 electrochemical response curve the temperature of the sensor should also be carefully controlled. When operating on or about the stoichiometric point, however, the output is substantially stable over a wide temperature range, i.e., from about 800°C to 1400°C, and therefore temperature control in the combustion chamber is not critical. In fact, the relative size of the
combustion chamber - The Zr02 sensor of Figures 1 and 2 can be stabilized with amounts of CaO or Y203 to further stabilize the temperature related response and to enhance the chemical and physical stability of the Zirconium Oxide for use as a sensor. This results in a stable sensor which possesses almost a step- change response at, or about the point of mixture stoichiometry.
- As can be seen from the embodiment of Figure 2, the fuel flow rate can be accurately controlled by the
motorized needle valve 114 in conjunction with theorifice 115. The air, of course, is also suitably pressure regulated as seen in that figure. After the fuel and air are mixed and burned in thechamber 122, thesensor 124 is used in conjunction with the electronics to achieve and maintain substantially stoichiometric proportions for the combustion of the sample gas by controlling the fuel flow. -
Claims (8)
Applications Claiming Priority (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/244,539 US4359284A (en) | 1981-03-17 | 1981-03-17 | Method and apparatus for determining the Wobbe index of gaseous fuels |
US244538 | 1981-03-17 | ||
US06/244,537 US4382698A (en) | 1981-03-17 | 1981-03-17 | Combustible gas analyzer |
US06/244,538 US4380400A (en) | 1981-03-17 | 1981-03-17 | Combustible gas analyzer |
US244537 | 1981-03-17 | ||
US244539 | 1981-03-17 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0060681A1 EP0060681A1 (en) | 1982-09-22 |
EP0060681B1 true EP0060681B1 (en) | 1987-01-21 |
Family
ID=27399772
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19820301229 Expired EP0060681B1 (en) | 1981-03-17 | 1982-03-11 | A combustible gas analyzer |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0060681B1 (en) |
DE (1) | DE3275237D1 (en) |
Families Citing this family (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4415278A (en) * | 1982-02-08 | 1983-11-15 | Honeywell Inc. | Method for operating a gas analyzing system and apparatus utilizing the same |
US4511262A (en) * | 1982-10-06 | 1985-04-16 | Honeywell Inc. | Fuel entrained oxygen compensation for calorific content analyzer |
DE3408397A1 (en) * | 1984-03-08 | 1985-09-19 | Ruhrgas Ag, 4300 Essen | METHOD AND ARRANGEMENT FOR DETERMINING THE MIXING RATIO OF A MIXTURE CONTAINING OXYGEN CARRIER GAS AND A FUEL |
FR2564591B1 (en) * | 1984-05-18 | 1988-01-15 | Siderurgie Fse Inst Rech | COMBURIMETER AND METHODS OF USE FOR DETERMINING FUEL POWER AND THE FUEL COMBURITY INDEX |
NL8802336A (en) * | 1987-12-05 | 1989-07-03 | Nederlandse Gasunie Nv | METHOD FOR DETERMINING THE WOBBE INDEX OF A GAS MIXTURE |
FR2626673B1 (en) * | 1988-01-29 | 1994-06-10 | Gaz De France | METHOD AND DEVICE FOR MEASURING THE HEAT POWER OF A VEHICLE BY A FUEL CURRENT |
NL8901660A (en) * | 1989-06-30 | 1991-01-16 | Nederlandse Gasunie Nv | METHOD AND APPARATUS FOR DETERMINING THE WOBBE INDEX. |
US5074987A (en) * | 1990-01-24 | 1991-12-24 | Elsag International B.V. | Online energy flow measuring device and method for natural gas |
US5288149A (en) * | 1992-03-12 | 1994-02-22 | Panametrics, Inc. | Gas calorimeter and wobbe index meter |
DE202007004675U1 (en) * | 2007-03-30 | 2008-08-28 | Robert Bosch Gmbh | Control device for a gas burner and gas burner |
EP2275811B1 (en) * | 2009-07-13 | 2011-10-26 | ELTRA Entwicklungs- und Vertriebsgesellschaft von elektronischen und physikalischen Geräten mbH | Device for determining the composition of a sample, particularly one containing protein |
CN102445465B (en) * | 2011-09-21 | 2012-10-24 | 周磊 | Chemical gas phase risk detection system with pressure-resistant and corrosion-resistant sealing device |
CN106501445B (en) * | 2016-12-24 | 2019-03-05 | 天津达元吉科技有限公司 | A kind of liftable oxygen index (OI) tester |
CN111366609A (en) * | 2020-03-15 | 2020-07-03 | 莱浦顿(上海)工程技术有限公司 | Combustible gas analyzer |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1361936A (en) * | 1963-03-06 | 1964-05-29 | Air Liquide | Apparatus for the analysis of gas mixtures |
IT1027899B (en) * | 1974-01-04 | 1978-12-20 | Heimke G | ARRANGEMENT FOR MEASURING THE OXYGEN CONTENT IN COMBUSTION GAS CHANNELS |
CA1083381A (en) * | 1976-05-03 | 1980-08-12 | William H. Clingman, Jr. | Method of and means for accurately measuring the calorific value of combustible gases |
US4134289A (en) * | 1977-11-03 | 1979-01-16 | Bailey Meter Company | Gas sampling system having a flow indicator |
NL7808476A (en) * | 1978-08-16 | 1980-02-19 | Nederlandse Gasunie Nv | APPARATUS FOR DETERMINING A QUANTITY CORRELATED TO THE WOBBE INDEX OF A GAS OR GAS MIXTURE, AND A METHOD FOR USING THIS APPARATUS. |
-
1982
- 1982-03-11 DE DE8282301229T patent/DE3275237D1/en not_active Expired
- 1982-03-11 EP EP19820301229 patent/EP0060681B1/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
DE3275237D1 (en) | 1987-02-26 |
EP0060681A1 (en) | 1982-09-22 |
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